The invention relates to a process and apparatus for feeding hydrocarbon feed to be contacted with catalyst. A field of the invention may be the field of fluid catalytic cracking (FCC).
FCC is a hydrocarbon conversion process accomplished by contacting hydrocarbons in a fluidized reaction zone with a catalyst composed of finely divided particulate material. The reaction in catalytic cracking, as opposed to hydrocracking, is carried out in the absence of substantial added hydrogen or the consumption of hydrogen. As the cracking reaction proceeds substantial amounts of highly carbonaceous material referred to as coke are deposited on the catalyst to provide coked or carbonized catalyst. This carbonized catalyst is often referred to as spent catalyst. However, this term may be misconstrued because the carbonized catalyst still has significant catalytic activity. Vaporous products are separated from carbonized catalyst in a reactor vessel. Carbonized catalyst may be subjected to stripping over an inert gas such as steam to strip entrained hydrocarbonaceous gases from the carbonized catalyst. A high temperature regeneration with oxygen within a regeneration zone operation burns coke from the carbonized catalyst which may have been stripped.
FCC can create a variety of products from heavier hydrocarbons. Often, a feed of heavier hydrocarbons, such as vacuum gas oil, is provided to an FCC reactor. Various products may be produced, including a gasoline product and/or light olefins, such as at least one of propylene and ethylene. To produce more light olefins, product cuts from FCC effluent, such as naphtha, may be recycled to the riser reactor or to an additional riser reactor for additional catalytic cracking These product cuts may be fed to the riser in a gaseous phase. Feed distributed to the riser in liquid phase is typically vaporized upon injection into the riser.
A problem encountered during the FCC process is distributing the feed in the riser so that it can adequately mix with the catalyst. Adequate mixing is usually necessary for efficient conversion of the feed. Hydrocarbon feed distributors spray dispersion steam and hydrocarbon feed into the riser typically transversely to a flowing stream of catalyst that is propelled upwardly by a fluidizing, lift gas. A relationship between injected feed velocity, drop size and momentum limits the horizontal travel of the injected hydrocarbon feed against the lift gas and catalyst accelerating vertically, upwardly in the riser. Additionally, a dense core of catalyst may develop in the axial center of the riser that resists penetration by the vaporous hydrocarbon feed. Larger riser diameters may exacerbate this problem because of the inherent difficulty in distributing the feedstock further toward the center of the riser.
Recycled feeds such as lighter hydrocarbon feeds derived from fluid catalytic cracked products may be recycled or fed to a reactor riser in vaporous phase. Penetration of vaporous feed into a flowing stream of catalyst is also difficult because of the lower density of the vaporous feed.
It may be desirable to provide a distributor for distributing hydrocarbon feed and catalyst to an FCC reactor from the same location.